1. Field of the Invention
The present invention relates to a technique to adjust the display luminance of a screen of a display apparatus according to ambient brightness.
2. Description of the Related Art
Many portable display apparatuses, such as a mobile phone, a digital camera, and a music player, are currently provided with a display that displays a menu screen and a captured image. The visibility of these portable display apparatuses significantly depends on ambient brightness. For example, when the display luminance of a display apparatus is kept constant, at an outdoor bright location, display brightness is insufficient and this may make the display difficult to view, and at an indoor dark location, display is too bright and this may make the display difficult to view. Accordingly, the ability to adjust the display luminance of a display apparatus in response to ambient brightness is preferable.
Japanese Patent Application Laid-Open No. 5-241512 discusses a technique to detect ambient brightness with a photometry sensor provided around a display apparatus and to adjust display luminance according to the detected value.
However, ambient illuminance significantly varies with the orientation of a display apparatus. Thus, in the technique discussed in Japanese Patent Application Laid-Open No. 5-241512, for example, when a portable display apparatus is moved while displaying an image thereon, display luminance may change frequently with a change in ambient illuminance.
Japanese Patent No. 03986278 discusses a technique to adjust the rate of change in display luminance of a display apparatus based on the size of a deviation between the current display luminance of the display apparatus and a desired display luminance to be determined by ambient illuminance. When the deviation between the desired display luminance and the current display luminance is large, a long period of time is required until the display luminance changes. Accordingly, a sudden change in display luminance due to a change in ambient illuminance can be prevented.
However, according to the technique discussed in Japanese Patent No. 03986278, the larger a deviation between the desired display luminance and the current display luminance, the longer a period of time is required until an appropriate display luminance is provided relative to ambient illuminance. Thus, when a user intends to view the display immediately after performing a certain operation, for example, to confirm a captured image with a digital camera, an appropriate display luminance may not be provided according to the conventional technique, so that visibility may deteriorate.